Many alternative solvents have been proposed to replace perchloroethylene. Liquid carbon dioxide is one example, but the high-pressure equipment needed for this inorganic solvent makes it unpractical and prohibitively expensive. A novel and more promising class of dry cleaning solvents are the so-called non-flammable, non-chlorine containing organic solvents. Examples may include hydrofluoroethers such as nonafluoromethoxybutane and nonafluoroethoxybutane or hydrofluorocarbons as decafluoropentane. Hydrofluoroethers are relatively low in toxicity, are claimed to have zero ozone depletion potential, have relatively short atmospheric lifetimes, and can have very low global warming potentials relative to chloro fluorocarbons and many chloro fluorocarbon substitutes. Furthermore, HFEs are listed as non-volatile organic compounds by the EPA, and as such are not considered as smog precursors.
Some dry cleaning processes have been proposed for application in residential homes. However, commercialisation thereof has been hampered by the prohibitive costs of the amount of clean solvent that is needed. Some proposals have been made to purify the used solvent, e.g. WO-A-01/94679, to decrease the amount of clean solvent that is needed. But purification is cumbersome and requires complicated machinery. It is costly, time and energy consuming because all residues need to be removed before the solvent can be safely used for cleaning laundry. In addition, solid waste is generated which requires adequate disposal to protect the environment.
Therefore, there is a need for an improved dry cleaning process that solves one or more of the aforementioned problems.
Surprisingly, we have now found an improved dry cleaning process for the in-home dry cleaning of laundry articles that overcomes one or more of the above mentioned drawbacks provided that a low grade non-flammable non-chlorine containing organic dry cleaning solvent comprising squalene is used. Low grade is meant to describe a solvent comprising at least 0.1 ppm, preferably at least 1 ppm, more preferably at least 10 ppm and most preferably at least 50 ppm, and less than 50 000 ppm, preferably less than 25 000 ppm, more preferably less than 10 000 ppm of squalene. A squalene level in the low grade dry cleaning solvent of less than 5000 ppm is most preferred.
While low grade dry cleaning solvent comprises squalene, surprisingly it is still effective in cleaning textile articles without causing colour changes over time. Low grade dry cleaning solvent is easier and more cost effective to produce because less pure material is needed and fewer purification steps are needed. Low grade dry cleaning solvent can also be produced from used dry cleaning solvent without the time, energy and solid waste production associated with prior art purification processes.